Drivetrain Wear and Chain Stretch

Hey im just goin shoppin for a chain tool to tell me wear on my chain cuz i kno im supposed to change them beyond 1% but i was wonderin how u kno when to change ur cassette, or chain rings, or derailleurs cuz those teeth wear down but how far before its unsafe. Like i have a 2000 Kona that well i admit hasnt been maintained well but thats like my corner store bike. The sprockets on the deraillers are worn pretty good yet it shifts and ride beautifully.

Hey im just goin shoppin for a chain tool to tell me wear on my chain cuz i kno im supposed to change them beyond 1% but i was wonderin how u kno when to change ur cassette, or chain rings, or derailleurs cuz those teeth wear down but how far before its unsafe. Like i have a 2000 Kona that well i admit hasnt been maintained well but thats like my corner store bike. The sprockets on the deraillers are worn pretty good yet it shifts and ride beautifully.

Seems like there is 2 theories here

1) Replace chain very often to keep cassette and chainrings fresh. This can be more costly and sometimes the new chain will not play well with the slightly worn cassette or chainrings.
2) Replace chain/cassette together after a year or so, longer if you don't ride as much. You can wear out your most used chainring(usually middle) quicker this way because the chain is used longer and stretched slightly more. The chainring teeth will look like shark fins if they are worn out.

I have tried both ways and I like the second method. Either way, the der. pulleys should last a few years and your chain is toast if it is stretched an 1/8" over a 12'' length of the chain(pin to pin)

If you haven't maintained it until now and everything is kind of wore out but it rides and shifts fine, why not just ride it till it don't ride good no more... then replace everything at once. A new chain on some wore out cassette/rings ain't gonna run so well. But if they ain't wore out just throw on a new chain, it's a cheap investment to help prolong drivetrain life. When the rings wear out, the U between the teeth ain't so much like a U no more, one side becomes steep and the other shallow.

Hey im just goin shoppin for a chain tool to tell me wear on my chain cuz i kno im supposed to change them beyond 1% but i was wonderin how u kno when to change ur cassette, or chain rings, or derailleurs cuz those teeth wear down but how far before its unsafe. Like i have a 2000 Kona that well i admit hasnt been maintained well but thats like my corner store bike. The sprockets on the deraillers are worn pretty good yet it shifts and ride beautifully.

That 1% should be closer to .5% if you want to keep riding the same cogs and rings. .5% corresponds to 12-1/16" across 24 links. Once you reach 12-1/8", the cassette is toast and the rings probably are as well.

The chain tools are handy, but a ruler is still more accurate. I use a Rohloff chain checker, but Park has a copy of that one that's probably more easily available called the CC-2. Avoid Park's old CC-1.

I use a Rohloff but when it gets close, I double check with a ruler. The good news is that the Rohloff and Park tools err on the side of caution, so they'll cause you to throw out a good chain rather than ride with a bad chain.

Rohloff make a cassette cog checker tool, which I owned for a short time. It's handy, but it's not worth it. The simple fact is, you know when the cassette is ready for replacement because of the way the chain dances between cogs. Even with regular chain replacement, it'll wear eventually.

Rings are harder to tell but the teeth will develop a "shark fin" appearance and shifting will turn to crap. Typically I'll get more life out of a chainring compared to a cassette, but again this is contingent on regular chain replacement based on the .5% wear mark.

a 3rd theory

Try using 2 chains with your bike and switch them every 500 miles or so. This way both chains and the cassette will wear at about the same rate. Then you dont have to deal with the somewhat worn cassette with a new chain if you decide to keep the cassette for longer than 1 chain.

I think a mileage based rules of thumb is tough to come up with. Rather than asking for mileage intervals, it's more accurate to use the 12-1/16" chain replacement method, and try to match a cassette and chainring replacement interval "every X number of chains".

Reason being that, while cogs and rings will wear regardless of chain condition, it's got to be largely dependant on how you ride. Someone who climbs a lot will likely require a cassette in fewer miles than someone who rides primarily on flats. Someone who charges up hills in the middle ring is going to wear their cassette down in fewer miles than someone who leisurely climbs in granny. And of course, someone who rides fast on the flats and spends much time in the 11-13T cogs can't help but grind those things down in no time.

On my wife's derailleur bike, her chains and cassettes lasted an eternity because she was never a very powerful rider, but her middle ring needed replacement not because of tooth wear, but because of abusive, low cadence shifting.

So assuming that the chain rate of wear somewhat follows how hard it's being ridden, you might come up with a rule that says "cassette & middle ring every 3rd chain".

I bought a little cassette cog guage from Rohloff called the "HG-IG Check" (or something like that). It's a mini chain whip with a calibrated end roller that, when wrapped around the cog, will either flip up off the tooth (cog OK) or will become "stuck" behind the tooth and won't budge (cog worn). I used it for a short period of time, and while it worked, I realized that it really wasn't telling me anything more that a new chain on an old cassette that "dances". So I sold off the cog checker, threw my replacement interval rules of thumb out the window, and simply began replacing cassettes whenever the new chain began to dance (which still worked out to about three chains per cassette).

I agree. 1000mi to someone who rides dry dirt singletrack and is anal about lubing and cleaning their chian will be far different from 1000mi to someone who rides thru muck, mud, rain, sand, etc and rarely takes care of their chain.

threw my replacement interval rules of thumb out the window, and simply began replacing cassettes whenever the new chain began to dance (which still worked out to about three chains per cassette).

Even though I, too, actually follow the 12-1/16" chain replacement method myself, I was just wondering about the easy/general "replacement every X number of chains" rule to keep in mind. (Sorry, not the over-simplified "500 miles" so much, per se.)

It's just that my XT cassette is on a fresh 3rd chain, and all are still working fine together, which actually started to make me wonder/worried, "Is this too good to be true!?" It must be my easy grannie pedaling...

With the 12-1/16" rule of chain replacement, I'll just "play by ear" (with my mind at ease) about the cassette/rings replacement - that's perfect.

Thanks again,
- PiroChu

PS...
If/when a new chain skips on used cassette & rings, how do I determine whether it's the cassette or the rings, or both? (Does the chain skip differently?)